← 14 15 16 →
Cardinalfifteen
Ordinal15th
(fifteenth)
Numeral systempentadecimal
Factorization3 × 5
Divisors1, 3, 5, 15
Greek numeralΙΕ´
Roman numeralXV
Binary11112
Ternary1203
Senary236
Octal178
Duodecimal1312
HexadecimalF16
Hebrewט"ו (Tet Vav)

15 (fifteen) is the natural number following 14 and preceding 16.

Mathematics

M = 15
The 15 perfect matchings of K6
15 as the difference of two positive squares (in orange).

15 is:

Furthermore,

2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397 (sequence A020994 in the OEIS)

Science

Seashells from the mollusk Donax variabilis have 15 coloring pattern phenotypes.

Religion

Sunnism

The Hanbali Sunni madhab states that the age of fifteen of a solar or lunar calendar is when one's taklif (obligation or responsibility) begins and is the stage whereby one has his deeds recorded.[9]

Judaism

References

  1. ^ Sloane, N. J. A. (ed.). "Sequence A001358 (Semiprimes (or biprimes): products of two primes.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  2. ^ Sloane, N. J. A. (ed.). "Sequence A001748 (a(n) = 3 * prime(n))". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  3. ^ Sloane, N. J. A. (ed.). "Sequence A000110 (Bell or exponential numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  4. ^ Sloane, N. J. A. (ed.). "Sequence A000332 (Binomial coefficient binomial(n,4) = n*(n-1)*(n-2)*(n-3)/24)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  5. ^ Sloane, N. J. A. (ed.). "Sequence A000384 (Hexagonal numbers)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  6. ^ Sloane, N. J. A. (ed.). "Sequence A051867 (pentadecagonal numbers.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  7. ^ Sloane, N. J. A. (ed.). "Sequence A334078 (a(n) is the smallest positive integer that can be expressed as the difference of two positive squares in at least n ways.)". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation.
  8. ^ H.S.M. Coxeter (1954). "Regular Honeycombs in Hyperbolic Space". Proceedings of the International Congress of Mathematicians. 3: 155–169. CiteSeerX 10.1.1.361.251.
  9. ^ Spevack, Aaron (2011). Ghazali on the Principles of Islamic Spiritualit. p. 50.

Further reading